Hydrogen sulphide gas, or H2S, is colourless in nature. This gas, often known as sour gas, sewage gas, and other nicknames, is both toxic and corrosive.
Surely you are not anticipating a pleasant odour from this gas! Well yeah, you are right, hydrogen sulphide gas stinks like rotten eggs!!
H2S has a molar mass of 34.08 g/mol and a density of 1.36 g dm-3. The melting point and boiling point of H2S are, respectively, -82°C and -60°C.
Because the sulphur atom completes its octet by sharing two electrons with two hydrogen atoms, H2S has a covalent connection.
In addition, I have written specifically about it; see the post on the covalent bonds of H2S.
Let us verify these foundations using the H2S Lewis structure description.
H2S Lewis Structure
Below is the Lewis structure of H2S.
To comprehend this, we must first grasp how to draw a Lewis structure.
Priority number one is determining the number of valence electrons present in the molecule.
The valence electrons in this molecule will be as follows:
Hydrogen valence electron = 1
2* Hydrogen atom = 2
Sulfur’s valence electron = 6
Consequently, total valence electron = 2 plus 6 = 8
The next step will be to identify the core atom.
Essentially, the central atom is the atom with the greatest number of bonding sites. In this case, the centre atom is sulphur.
After locating the core atom, we must draw the skeletal structure of H2S using just single bonds.
It’s useful to note that lewis structure is all about atoms and electrons completing their octet. Every atom attempts to complete its octet in order to achieve stability.
In this molecule, sulphur has six electrons, thus it need two more electrons to attain an octet, or eight electrons. Similarly, the octet of hydrogen’s 1s shell can only be filled with two electrons.
Hydrogen requires only one additional electron to achieve stability.
After forming single bonds in the sketch, the next step in drawing the Lewis structure of H2S will be to fill in the remaining electrons surrounding the sulphur atom.
To complete the Lewis structure of H2S, it is necessary to verify that all atoms have the lowest feasible formal charge.
To make learning how to design a Lewis structure a little less complicated, I have outlined the stages below.
Determine the total number of valence electrons in the molecule in the first step. Consider the + and – signs when performing calculations.
Choose a core atom, which is typically the atom with the most bonding sites.
Draw a skeleton framework using only single bonds in the third step.
Fill the octet of the atoms with the remaining electrons in step four. Remember to begin with the electronegative atoms and then go on to the electropositive ones.
Step 5: Provide numerous bonds if necessary to complete the octet of the atoms.
Step 6: Finally, ensure that each atom has the lowest feasible formal charge. This can be calculated using the formula shown below.
Let’s shed some light on H2S hybridization before moving on to the next topic!
H2S has no hybridization according to Drago’s rule.
Drago’s Rule – This rule asserts that there is no mixing of orbitals, or hybridization, when the energy difference between the atomic orbitals is too great.
Thus, there will be no central atom hybridization. The following requirements must be met for this regulation to go into effect:
The central atom must be in the third period or lower, with at least one lone pair.
The electronegativity of the surrounding atoms should be less than or equal to 2.5.
The centre atom should be devoid of positive charge.
This rule applies to six compounds, including PH3, AsH3, SbH3, H2S, H2Se, and H2Te.
Certainly, H2S fulfils all requirements.
Sulfur, the centre element, belongs to the third period, has two lone pairs and no positive charge. In addition, hydrogen’s electronegativity is 2.1.
This explains why H2S is incapable of hybridization.
Adding to this rule is the fact that the energy gap between the unoccupied orbital of Sulfur and the 1s orbital of Hydrogen is enormous.
Therefore, no hybrid orbital formation exists. Consequently, this is another theory stating that H2S does not hybridise.
H2S Geometrical Structure
H2S’s molecular geometry is curved.
The tetrahedral electron shape of H2S is another crucial aspect. Before we get into the distinction between these two, let’s examine how to locate them.
Therefore, both geometries may be determined using the VSEPR table. The graph is appended below!
This graphic reveals that H2S is a molecule of the type AX2E2, where X represents the atoms around the central atom and E indicates the lone pairs of the centre atom.
Thus, we might say that H2S has a curved molecular geometry.
The distinction between electron geometry and molecular geometry is next.
When establishing the shape of molecules, molecular geometry primarily considers solely their constituent atoms. In contrast, electron geometry takes into account all electrons present.
The significant difference between the two shapes is due to the fact that the latter takes the solitary pair into account.
Keep in mind that the repulsion between the two lone pairs in H2S also plays a significant influence in its curved molecular shape.
The repulsion transforms straight bond pairs into curved ones.
All of these describe the atomic geometry of H2S.
H2S Molecular Orbital (MO) Diagram
The diagram of H2S’s molecular orbitals can be explained as follows.
This is the H2S MO diagram. The left side will contain the sulphur atomic orbitals, 3s2 3px2 3py1 3pz1.
And on the right-hand side will be hydrogen atomic orbitals.
In the MO orbitals, 8 valence electrons are present. There are also two orbitals that do not form bonds. The anti-bonding orbitals are empty, but the bonding orbitals are full.
From an H2S MO diagram, we may determine the bond order, bond length, and bond stability of the molecule.
Additionally, it must be remembered that the unoccupied orbitals of sulphur and the 1s of hydrogen have a significant energy difference. But the MO diagram can also be constructed afterward!
Let’s also examine the preparation procedures for H2S in the section below.
Polarity of hydrogen sulphide
The H2S molecule is believed to be a polar molecule due to its curved form. The dipole moments across both H-S bonds do not cancel each other out, resulting in a net dipole moment.
I request that you read the article on the polarity of H2S for further information.
Preparation of H2S
Hydrogen sulphide can be created in numerous methods, including the following:
The most prevalent method is the preparation of sour gas (any gas having high H2S content).
Hydrogen sulphide can be produced by reacting hydrogen with 450°C sulphur elemental molten in a furnace.
In the Kipp generator, ferrous sulphide is reacted with a strong acid.
FeS + 2HCl ——-> FeCl2 + H2S
Another qualitative analysis used thioacetamide to generate H2S.
CH3C(S)NH2 + H2O ———> CH3C(O)NH2 + H2S
6 H2O + Al2S3 ——–> Another process for the generation of hydrogen sulphide is 3H2S + 2 Al(OH)3.
Now, it is common knowledge that H2S is employed in several processes to generate various chemicals.
Hydrogen sulfide’s structure, bonding, and hybridization, as described previously, are prerequisites for a clear comprehension of these processes.
This article discusses the lewis structure, hybridization, and bonding of H2S. These facts are crucial to comprehend in order to understand H2S-related equations efficiently.
I hope that after reading this text, you have got some understanding of this substance. Even though there is much more to learn, it is best to proceed gradually! Ultimately, chemistry is a broad field!
If you have any questions on any of the topics discussed in this essay, please free to contact me at any time.